The present invention relates to commercial carbon fiber-filled sheet molding compound having light weight, high stiffness, and high strength.
The process of compression molding has grown to be ever so common. The product used in and produced by the process of compression molding is termed sheet molding compound or SMC. Compression molding was developed for replacement of metal components with composite parts. The molding process is typically carried out with either thermosets. Typically, a thermoset charge is placed in a two-piece heated mold which is subsequently closed and held at a high pressure. This initiates a thermal setting cure reaction. Typical products manufactured by compression molding include front and rear end vehicle panels, hoods, roofs, fenders, spoilers, and air deflectors.
Many SMC products are filled with fibers, such as glass fibers. Glass fibers provide strength and stiffness. U.S. Pat. No. 5,484,652 to Strunk et al. involves a material for smoothing the outside surface of a woven fabric composite lay up in which a layered sandwich structure is formed of continuous fiber woven material, resin films and a mat of randomly oriented discontinuous fibers. The sandwiched layers are integrated into a single sheet of resin impregnated material by application of pressure and heat.
However, costs for painting or coating glass fiber-filled SMC products can be reduced. Typically, a conductive primer is applied onto glass fiber-filled SMC products before color painting or coating the product. The conductive primer provides for the ability to electrostatically paint or coat the SMC product. Because glass fiber-filled SMC products are not conductive, without application of conductive primer onto the SMC product, subsequent painting or coating onto the product would result in a low efficiency paint transfer upon the product surface. This results in higher costs and increased time of production. If the manufacturing step of applying conductive primer onto the SMC product can be eliminated, then substantial cost savings would be experienced.
Moreover, as the price of glass fibers remains stagnantly high and the price of automotive carbon fibers continues to decrease, feasibility and demand to use automotive carbon fibers in lieu of glass fibers in SMC products grow. Generally, carbon fibers are more expensive than glass fibers, but add greater strength and stiffness when used in SMC products. Carbon fibers are also lighter weight than glass fibers at comparable fiber loading.
What is needed is an automotive carbon fiber-filled SMC product that provides for electrostatically painting or coating the product without applying a conductive primer.
What is also needed is a method of making a carbon fiber-filled SMC that has high stiffness and strength.
It is an object of the present invention to provide an improved method of making automotive carbon fiber-filled SMC that is lighter weight than glass fiber-filled SMC at comparable fiber loadings.
It is another object of the invention to provide an improved SMC that provides for electrostatically coating or painting directly thereon without applying a conductive primer.
It is yet another object of this invention to provide an improved method of making a carbon fiber-filled SMC that has high stiffness and strength.
A more specific object of this invention includes a method of making from laminate an automotive carbon fiber-filled sheet molding compound having the characteristic of light weight, high stiffness, and high strength. The method comprises providing chopped automotive carbon fibers, a predetermined resin paste, a first carrier film, and a second carrier film. The method further comprises coating substantially completely one side of one of the first and second carrier films with the predetermined resin paste to define a coated side, depositing the chopped automotive carbon fibers onto the coated side, and covering the deposited carbon fibers with the second carrier film to define a compatible carbon-filled laminate. The method further comprises compacting the carbon-filled laminate to admix the resin paste with the carbon fibers between the films, whereby to form the automotive carbon fiber-filled sheet molding compound.
Another more specific object of this invention includes an automotive carbon-filled sheet molding compound having the characteristics of light weight, high stiffness and high strength. The compound is manufactured by providing chopped automotive carbon fibers, a predetermined resin paste, a first carrier film, and a second carrier film. The process by which the sheet molding compound is manufactured further includes coating substantially completely at least one of the opposed sides of the carrier films with the predetermined resin paste to define coated sides of the first and second carrier films, depositing the chopped automotive carbon fibers onto the coated side of the first carrier film, and covering the deposited carbon fibers with the coated side of the second carrier film to define a compactable carbon-filled laminate. The process by which the compound is manufactured further comprises compacting the carbon-filled laminate to admix the resin paste with the carbon fibers disposed between the films, whereby to form the compound.
Yet another more specific object of this invention includes an automotive carbon-filled compound being lightweight and having high stiffness and strength, the carbon-filled compound produced by the process of manufacturing sheet molding compound.
Another more specific object of this invention provides for a system for making from laminate an automotive carbon fiber-filled sheet molding compound having the characteristics of light weight, high stiffness, and high strength. The system comprises a first mechanism for providing chopped automotive carbon fibers, a predetermined resin paste, a first carrier film, and a second carrier film. The system further includes a second mechanism for coating substantially completely one side of one of the first and second carrier films with the predetermined resin paste to define a coated side, a third mechanism for depositing chopped automotive carbon fibers onto the coated side, and a fourth mechanism for covering the deposited carbon fibers with the second carrier film to define a compactible carbon-filled laminate. The system further comprises a fifth mechanism for compacting the carbon-filled laminate to admix the resin paste with the carbon fibers between the films, whereby to form the automotive carbon fiber-filled sheet molding compound.